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Hidden Text in Images

Text can be hidden by making it nearly invisible (turning down it's opacity to below 5%) or using certain colors and filters on it. Although the text is indiscernible to the naked eye, it is still there, and there are a variety of tools which allow the text to be extracted.

Use

  • Create

    * Watermark example in GIMP

  • Find

    * GIMP or Photoshop can be used to uncover the flag by using different filters and color ranges, as shown in the same watermark guide as above.

    * Stegsolve is an immensely useful program for many steganography challenges, allowing you to go through dozens of filters to try to uncover hidden text.

    * There are many scripts that have been written to substitute certain colors and make hidden the text legible, for example this Ruby script highlights colors passed to it in the image.

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